After a well hole has been drilled and a casing has been cemented in place lining the well hole, various tools are "tripped", or lowered, down the cased hole to perform various functions in the well hole. While the tools perform their function they often need to be secured inside the casing at a certain point. An example of such a tool is a gravel pack tool which is used to provide a screen to filter out sand from oil being produced from a formation. When oil flows from certain formations into the casing, sand can slough off from the formation and travel with the oil into the casing, this causes premature wearing and damaging of oil field production equipment. Gravel packing tools have been developed to pack gravel around a screen disposed in the well hole proximate the producing formation. This packed gravel prevents the sand in the producing formation from traveling with the oil into the well hole casing.
A gravel pack tool is "tripped" down the hole on a service tool assembly. The gravel pack tool and the service tool assembly together are referred to as a gravel pack system. The service tool assembly typically comprises a cross-over tool, which is used in depositing the gravel slurry around the screen, and a setting tool, which is used to set the gravel pack tool inside the casing. The gravel pack tool is typically connected to the service tool assembly by either a left-hand square thread or some type of shearing device which shears upon a pulling up of the work string.
After the gravel pack tool has been lowered to the desired position proximate a producing zone, the setting tool is activated to set the gravel pack tool inside the casing. Also, the producing zone proximate the gravel pack tool must be isolated from the remainder of the cased hole. This setting and isolation is achieved by setting packers above and below the gravel screen of the gravel pack tool. The bottom packer is typically tripped down the hole before the gravel pack tool and set into the casing. This bottom packer is commonly referred to as a sump packer. A typical packer has an elastomeric circular ring which is radially extended to seal circumferentially with the inside of the casing. Packers also have a teeth element that bites into the side wall of the casing to 10 prevent any movement of the packer in the casing. The sump packer seals the well hole below the gravel pack tool so no oil being produced travels down the well hole. After the sump packer is in place, the gravel pack tool is tripped down the hole until the bottom of the gravel pack tool engages and seals inside the sump packer.
The top packer is typically a part of the top of the gravel pack tool and is generally referred to as the gravel pack packer. The gravel pack packer is maintained in an unset position during "tripping" and then set into the casing by the setting tool of the service tool assembly when the gravel pack tool has been properly bottomed in the sump packer. Located immediately above the gravel pack packer and also on the gravel pack tool is a setting sleeve. The setting tool of the service tool assembly, typically upon hydraulic activation, engages with the setting sleeve which in turn pushes on the packer, setting the packer into the casing.
In crooked wells, highly deviated wells, horizontal wells, or wells with stepped casing, a tool being tripped down the well will often bind inside the casing at a sharp radius or an edge of stepped casing. In such a situation it is necessary to manipulate the work string back and forth and/or in a rotational manner to work the tool by the "tight spot". A danger in working a tool by a tight spot is that the setting sleeve above the packer could catch on the casing while the work string moves upward relative to the setting sleeve. Such movement can cause the sleeve to push on the packer thus prematurely setting the packer inside the casing. Premature setting of the packer jams the gravel pack tool in the casing out of position. Retrieving such a jammed tool is costly and time consuming. While the typical safety mechanism to prevent such a premature setting is the use of shear s crews in the setting sleeve, the shear screws can still be overcome by such manipulations through tight spots. Casing liner tops in horizontal wells can be particularly difficult to pass since tools tend to ride on the bottom side of the casing. Thus, a need exists to provide a mechanical lock on the setting sleeve to prevent premature setting of the gravel pack packer.
Such a lock should also be easily deactivated when it is desired to set the gravel pack packer. Manipulation of the work string to disengage the lock is undesirable because manipulation of the work string will be used to work the gravel pack tool past tight spots. Thus, a need exists to deactivate the lock without having to manipulate the work string.
Since work string rotation may be required to work tools by tight spots, there must be a rotational lock mechanism to transmit work string rotation to the gravel pack tool. But since the gravel pack tool is often connected to the service tool assembly with a left-hand square thread the rotational lock mechanism must be easily deactivated to enable the rotation of the service tool assembly out of engagement with the gravel pack tool. Again, manipulation of the work string would be an undesirable way to disengage a rotational lock thus a need exists for a rotational lock which can be hydraulically deactivated.
It would be preferable that one locking mechanism could both rotationally lock the gravel pack tool and lock the setting sleeve.
When the service tool assembly is rotated to disconnect from the gravel pack tool at the left-hand square thread, it is recommended that the string weight at the left-hand square thread approach neutral to prevent thread locking or frictional binding. Rig time is often wasted attempting to approach the neutral point, and establishing the neutral point in horizontal wells can become increasingly difficult due to work string-to-casing torque and drag problems. Thus, a need exists to eliminate having to find the neutral point to disengage the left-hand square thread.